Question about battery charging

i"m using below circuit to charge up my car battery, and i'm using solar panel as a power supply, is around 2A-3A as a output for solar panel, my charging voltage for car battery is around 14V-14.7V


i'm also using my car battery to power my electrolysis system at the same time (is around 7A needed), but not using all the time, while the charging system is in progress and i'm using the car battery to power my electrolysis at the same time, my charging voltage will drop to around 13V, will this spoil my car battery?anyone know about this?need any circuit to solve this problem?

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i'm using this for school project purpose, i want produce hydrogen through electrolysis.....anyone can help me?

When a car battery is supplying current and discharging, it's voltage will drop below 13V. This is normal and will not harm the battery. But for maximum battery life you generally don't won't to discharge it below 50% of it's capacity, unless it's a deep discharge type of battery (such as used on boat trolling motors).